Underwater adventuring has always been, insofar as Pathfinder is concerned, one of those ideas that seem great in theory but difficult in practice. After all, taking your adventuring party underwater means that everyone’s aware that one good dispel magic will take away whatever spells or magic items they’re using to keep breathing. Add in penalties for how melee and ranged attacks work, changes to spellcasting, and even the continual Swim checks to keep moving, and it’s not only a headache for everyone involved, but quite likely a TPK waiting to happen. And don’t even get me started on the logistics of fighting across three dimensions of movement.

And so, underwater adventuring was quietly pushed off to the side. Just enough rules were provided to make it theoretically possible, without anyone worrying about how practical it actually was. Few adventures were published that dealt with characters going into the waves, and those that were kept it to the shallow end of the pool, with dry land always being close by. Finding new paths under the sea seemed like it’d always be resigned the realm of pipe-dreams and a few die-hards, never to be accessible to the mainstream Pathfinder gamers.

All of that changed when Alluria Publishing released Cerulean Seas, a massive campaign setting-slash-sourcebook that not only takes Pathfinder underwater, but actually makes such a game doable. Let’s take a look at what the book offers so that you’ll know this isn’t just a fish story I’m telling you.

As a PDF file, Cerulean Seas hits all of the high-water marks. It has full, nested bookmarks (an absolute necessity in a book that’s nearly 300 pages long), and allows for copy-and-pasting without problems. And of course, the artwork – oh wow, the artwork! Alluria has always had a reputation for their lavish illustrations, and they certainly live up to it here. An entire team of interior artists have lovingly portrayed myriad aspects of the book’s material, from new races and monsters to new equipment, to spell effects, to a map of the Cerulean Seas area, and so much more, (almost) all of it in lush full color. Alluria is perhaps the only company that can compete with Paizo on an even footing for how gorgeous their books look.

Of course, this (and the subtle but ornate page borders) means that this book is far from printer-friendly. At the time of this writing, a print version of the book is still in the works, but isn’t yet available. If you want a hardcopy of Cerulean Seas, you might be better to wait for that, as this PDF would likely send your printer to Davy Jones’ Locker.

The book’s opening chapter dives right in, opening with framing fiction that defines the game world. The Cerulean Seas campaign setting used to be a normal game world, but had a great flood that covered the world with ninety-nine percent water. There’s more to it than this, of course, including a recently-won genocidal war against the sahuagin, the role the gods played in the great flood, and more, but this is the main thrust of the story, and sets the stage for this water world.

The chapter takes us through some basic terms and definitions before we start to get into the specifics of living under the sea. It’s here that the book might start to scare away some of the more casual-type gamers, because this chapter pulls no punches in what it presents. We’re given an introduction to how things like buoyancy, hydraulic pressure, ambient sunlight, and more work underwater. The first chapter is basically a primer for things to be aware of regarding life underwater, and how these translate into game terms. This is especially true for underwater combat, which has its own section here.

I’ll take a moment to say that while this section can be off-putting for how dry (ironically) its listing of various undersea features can be, as well as how complicated the rules for buoyancy and the accompany combat changes are, it’s worth persevering through. The book deals with this more in the Game Mastering section, but these are the changes that really make an undersea game feel different; and as with all parts of a complex table-top game, they’ll become more familiar (to the point of being second-nature) over time.

The second chapter returns to more familiar territory where PF sourcebooks are concerned, presenting twelve new undersea races (though one or two, such as sea elves or the mogogols, may seem familiar). Cleverly, these are sub-divided into three groups: the anthromorphs (who have humanoid bodies), the feykith (fey-related sea-dwellers), and merfolk (who are humanoid from the waist up, and fish from the waist down). Interestingly, the human-equivalent race is presented as the “seafolk,” a merfolk race. They not only have the human’s “floating” +2 ability bonus that can be applied everywhere, but are the only race to have various cross-breeds listed, with alternate racial traits presented.

Each race received a generous focus, listing not only their statistics but also plenty of flavor text regarding their society, alignment, possible names, etc. However, ardent Pathfinder fans may be somewhat disappointed that the expanded racial options from the Advanced Player’s Guide aren’t reproduced here. That is, there are no alternate racial features available (seafolk crossbreeds notwithstanding) nor are there alternate favored class options.

I’m of two minds about this, as it seems somewhat unfair that these have suddenly been assumed to be default necessities for third-party contributions to the Pathfinder RPG. At the same time, those bring a hefty level of customization to the table that are very helpful in making your character’s race be of greater importance. That said, twelve colorful new races here certainly make that notable in and of themselves. It’s also worth noting that the book doesn’t forget to bring us the various vital statistics for these races (one of those little things that are nevertheless important).

Subsequent to the races chapter is the chapter on classes, and it’s here where things get truly interesting. The book makes some generalized notes about changes to existing classes before dealing with how to alter each base class specifically for an undersea game. This part of the book does deal with the APG classes, so you alchemists and oracles and such can all breathe a sigh a relief.

The changes made in this regard are absolutes, rather than the optional class archetypes presented in the APG. Interestingly, a few classes are recommended to be discarded entirely in favor of three new base classes presented here. Bards are passed over in favor of sirens, druids are replaced with kahunas, and rangers are given the boot in favor of mariners.

These new classes do a great job presenting their own twist on the niche that their replaced classes fill. The Kahuna, for example, is a full-progression divine spellcaster, but selects a single animal spirit that, as she gains levels, is able to utilize greater and greater spirit powers to bolster herself and her allies (or alternately harm her enemies).

This chapter also deals with prestige classes, listing which ones from the Core Rulebook and APG are useable without any changes, which need some changes, and which aren’t available at all. There are also three new prestige classes presented here, the each comber (those who venture into the wilds of the remaining dry land), glimmerkeeper (fast-moving undersea hero), and sea witch (an aquatic necromancer).

Skills and feats are the subject of the fourth chapter. As with many things, the skills section offers a series of new interpretations of existing skills, though there are no new skills added (something I was grateful for, as adding new skills often feels contrived). The feats section got a similar examination for several existing feats, but here we’re given almost four-dozen new underwater feats as well.

The chapter on money and equipment was interesting for how much stayed the same, though quite a bit changed in appearance. Most precious metals have been replaced by things like shells or pearls, though the measurements of currency are largely the same. New equipment helps there be a greater selection of viable weapons and armor underwater, not to mention various items that are unique to undersea adventuring, such as holy sand to replace holy water. Oddly, ships are presented here also, reinforcing that some aquatic races still spend a lot of their time above the waves.

The magic chapter presents some very imaginative alterations to not only existing spells, but also existing material components and foci before it moves into new spells and magic items. Some of what’s here deals with the change from fire damage to boiling-water damage, while others present alternate ways of harnessing electrical spells, or various utility spells such as defeating undersea pressure, or even breathing air for characters who want to go top-side.

It’s at the seventh chapter of the book that we take a look at the Cerulean Seas campaign world. This chapter takes a surprisingly light tone with the campaign, presenting many different facets of it but not going too deep with any of them, letting you fill in a lot of the blanks to make the game world your own. It does cover the recent histories and major NPCs of all of the major races, presents a number of major cities, a brief overview of the spoken languages, and an overview of the world’s recent history. My favorite, however, was the presentation of the Cerulean Seas religions. The undersea races uniformly decided to prevent religious strife by allowing only nine deities to be worshipped, one for each alignment. However, in order to sweep everyone under this umbrella, there are various “cults” that worship different aspects of these deities (each deity has two cults presented, with their own alignments, domains, etc.). These cults may only operate with the blessing of the parent faith, and it was engrossing to read about how various races merged their native religions with that of a more dominant faith, often resulting in the major god literally consuming the smaller one as a consequence.

I don’t mind saying that chapter eight, the Game Mastering Chapter, was perhaps the most friendly and helpful such section I’ve ever read. It speaks frankly, and almost familiarly, about the problems with running an undersea game, and what to do about them. Remember those scary new rules from chapter one? It goes over what the most important are to get down pat and how to ease into them. We get general guidelines on converting other materials for an undersea game, whether in terms of buoyancy or pressure tolerance. But my favorite section here was the unabashed look at the problem of 3D combat.

The book outlines roughly a half-dozen options for what to do about this issue, ranging from buying commercial elevation trackers to ordering a pizza and using those little plastic things that keep the cheese off of the box to elevate your minis. But by far the most favored option it presents is the one where it walks you, step by step, through creating your own adjustable boards for elevation. These are basically a few square inches of hard foam boarding that are moved up and down a standing rod; add a half-dozen of them to your game table and you can easily simulate characters moving across every dimension. It’s a fun little project, and works great for any tabletop game that needs a 3D combat solution.

There’s also a fascinating section on the planar arrangement (or perhaps just the widespread belief in the arrangement) of this campaign world. After all, an undersea culture hardly believes in a plane of fire, especially one that stands equal to the plane of water! Likewise, the oceans of the outer planes are considered much more prominent than the dry areas of such realms.

The final full chapter of the book presents almost a hundred new monsters to help populate your undersea game. From aquatic familiars to a large selection of new giants and true dragons (which are given their own grouping, rather than being chromatic or metallic), there’s plenty here to round out an underwater bestiary. New selections of simple templates and guidelines on how the major creature types work underwater provide further options and guidelines.

The book closes out with a number of helpful aids, such as a consolidated list of undersea monsters from this book, the Pathfinder Bestiary, and Alluria’s other Pathfinder books. Add in a pronunciation guide, cardstock minis, a character sheet, and more, and there’s everything you’ll need to get started on your Cerulean Seas game right away.

And if you’re not already excited about using this book to run an underwater game after reading this review, then trust me: it’s more due to my descriptions lacking enough fidelity to the book’s accomplishments than anything else. Cerulean Seas not only looks at every aspect of running a game in an underwater world – from what it means to be submerged to the logistics of it at the game table – but presents holistic options and alterations for setting a Pathfinder game there. The new material is expansive and the campaign setting covers a wide range of topics while still leaving room for customization. And of course, the artwork is beautiful and prominent. This is easily one of the best Pathfinder books to come out of the third-party market, and the absolute best for the topic it covers.

Don’t be afraid to make your game better by taking it down where it’s wetter. Bring your characters to the Cerulean Seas; it’ll make a big splash amongst your gaming group.